a) Field of the Invention
The present invention relates to a compact pump (reciprocating pump) which uses a diaphragm.
b) Description of the Prior Art
A conventional compact pump of this kind, for example a pump disclosed by Japanese Patent Kokai Publication No. Sho 62-291484, has a configuration shown in FIG. 1.
In this conventional compact pump, a disk like driving plate 35 is mounted on a driving shaft 34 which is studded, at a predetermined inclination angle, to a crank base 33 which is fixed to an output shaft 32 of a motor 31. Single or a plural cup like diaphragm sections 36 which has upward openings are disposed on an outer circumferential portion of the disk like driving plate 35. In case of a pump which comprises a plurality of diaphragm sections 36, the diaphragm sections are arranged at equal intervals along a circumference. A reference numeral 37 represents a cylindrical valve which is integrated, for example, with the diaphragm section 36, a reference numeral 38 designates another valve, a reference numeral 39 denotes an inlet port and a reference numeral 40 represents an exhaust port.
When the output shaft 32 is rotated by driving the motor 31 in the compact pump, the crank base 33 are rotated and the driving shaft 34 is moved like a gooseneck, whereby roots 36a of the diaphragm sections are moved up and down. Accordingly, a cup like diaphragm 36 which is located on the left side in FIG. 1 is raised from a position where its root is lowered, whereas a diaphragm 36 which is located on the right side is lowered from a position where its root 36a is raised.
As the roots of the diaphragms 36 are moved up and down, the diaphragms suck and exhaust a fluid definite time intervals, thereby causing a pumping function.
In order to cause ideal reciprocal movements of the diaphragms 36 in the conventional compact pump described above, a center A of the driving shaft 35 which is located between the two diaphragm sections 36 must be aligned with a center axis of the output shaft. In other words, the center A must be located on an extension of the output shaft 32. In order to align the center A with the center axis of the output shaft 32, the driving shaft 34 must be equipped with a bearing, thereby prolonging the driving plate 35 and enlarging the pump as a whole.
Furthermore, a rotation of the output shaft 32 causes a reciprocal movement of a driven portion of the diaphragm 36. When a rotating frequency of the motor is enhanced to rotate the output shaft at a higher speed, the pump allows the diaphragm sections 36 to be abnormally deformed, thereby extremely shortening service lives of the diaphragms. Accordingly, the pump requires a large motor which exerts a strong force.